Modern high speed aircraft are equipped with escape systems with predetermined safe ejection envelopes as measured by acceptable speed, flight altitude, aircraft roll and pitch angles, and sink rate, as well as other factors such as seat and aircraft characteristics. If an ejection takes place within the safe ejection envelope of, for example, an ejection seat, aircrew can survive ejection even at the outer margins of an aircraft's flight envelope, including take-off, landing, and even zero altitude and zero air speed conditions. All existing aircraft escape systems are actuated manually, subsequent to aircrew evaluation of the circumstances leading to a decision to eject.
One of the most complex and demanding examples of vehicle escape system is found in high-speed military aircraft, such as jet fighters, attack craft and even bombers. In such military aircraft, the aircrew assesses a situation, and when ejection is believed to be warranted, one of the members of the crew will initiate the process of ejection. This will vary from aircraft to aircraft, depending upon the configuration of aircrew placement within the aircraft.
In conventional high-speed jet fighters, ejection is usually initiated by pulling on an ejection handle, squeezing an ejection handle or a similar device to initiate the ejection sequence.
Operation of the ejection process for a conventional ejection seat is highly automated after initiation of the ejection sequence by the aircrew. However, in conventional aircraft, ejection takes place only after the aircrew has gone through a decision-making process based upon perceived conditions of the aircraft or surrounding environment. This is crucial since the pilot (and other crew if the aircraft is so configured) must be able to clear the aircraft as quickly as possible, while at the same time avoiding hitting any part of the aircraft, or each other.
The relatively long aircrew decision process could be considerably shortened by an automatic ejection system. However, such systems have not been contemplated due to difficulties in providing a fail-safe against unintended ejections. Such ejections have severe consequences of leaving a plane without control, and endangering the ejected aircrew.
In certain types of modern aircraft various emergencies can develop so rapidly that aircrew have insufficient time to evaluate the situation and initiate ejection within the seat's safe ejection envelope. This is particularly relevant for short take-off vertical landing aircraft (STOVL) in “vertical” modes of flight (hover, short take-off, transition, vertical landing, when STOVL speed is less than control speed and aerodynamic forces are insufficient to support the aircraft in flight). Power plant or reaction control failures in these regimes lead to uncontrolled STOVL descent combined with violent rotation in roll and pitch. In such circumstances the time available for evaluation of the situation and initiation of ejection, within the ejection seat's safe ejection envelope, is not more than two or three seconds.
Another example of a rapidly developing emergency situation can be the failure of either the catapult or aircraft power plant during launch of aircraft carrier based aircraft. If the aircraft is insufficiently accelerated to achieve flight velocity, it settles into the water within 2 or 3 seconds after launch. Likewise, in conventional land based operations, while in transition just after take-off or prior to landing, the onset of rapidly developing emergencies that prevent or inhibit controlled flight, may not permit aircrew sufficient time to effect safe ejection.
Consequently, survival in rapidly developing irreversible emergencies could be significantly improved by the addition of an automatic system for initiating ejection from aircraft (as well as for a wide variety of vehicles). An automatic escape system, by providing an appropriate response for the detection of a catastrophic (irreversible, or unrecoverable) situation would eliminate the time required for pilot decision-making and ejection initiation from the ejection timeline.